Thank you guys for the reply. After two nights in front of the hex editor i actually managed to decrypt the files i need.
The format is similar but not exactly how Daniel Buscombe described it for other models. Some Bytes are still unknown but i got all i need for my master thesis. All data is unsigned and big endian.
DAT file:
64 Bytes
(1-20) - Spacer/unknown
(21-24) - UNIX Timestamp
(25-28) - UTM X
(29-32) - UTM Y
(33-42) - character - File Name
(43-44) - Spacer
(45-48) - number of rrecords
(49-52) - record length in milliseconds
(53-56) - line size
(57-64) - unknown
IDX file: - (time)(startbyte) points onto the record of a segment in the related .son file
(1-4) - time in ms since start of record
(5-8) - Byte at which position a new block starts
...repeat
SON file: contains the echo data. each new echo ping is a new block. each block has a header and the data behind. idx file points on the blocks
Block 1
(1-5) - always the same. indicates the start of a new block (192, 222, 172, 33, 128)
(6-9) - record Nr.
(7) - spacer
(11-14) - time in ms (same as in idx)
(15) - spacer
(16-19) - UTM X
(20) - spacer
(21-24) - UTM Y
(25) - spacer
(26-27) - gps good/ bad, 0/1
(28-29) - heading in °/10
(30)-spacer
(31-32) - ? water type? gps?
(33-34) - speed in cm/s
(35-40) - spacer
(41-44) - depth in cm
(45) - spacer
(46) - beam nr. (0=50/83khz, 1=200khz,2=port,3=starboard)
(47) - spacer
(48) - volt scale?
(49) - spacer
(50-53) - frequency (should be same as in byte 46)
(54-67) - spacer
(68-71) - length of each sentence (amount of bytes for each ping in data section)
(72) - spacer
NOW STARTES THE DATA its 8- bit integer unsigned -> a integer value between 0-255 (creates the shade of the grey of echogramm)
(73-1649) - thats the length of the data in my case. dont know if it varies over different measurements
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one block (ping) done now repeat with the next block starts with the header again and data after.
Hope this helps if someone.
Best wishes
Scaling